Past Climate is Window to the “Near Future” Arctic

The news last week was dominated by the announcement that the earth’s atmosphere has now reached a co2 level, 400 parts per million (ppm), a level not seen in millions of years.

The video above shows the cracks that opened in thinned and fragile arctic ice, even in the dead of winter this past february and march.

These news items are not unrelated.

NYTimes:

Scientific instruments showed that the gas had reached an average daily level above 400 parts per million — just an odometer moment in one sense, but also a sobering reminder that decades of efforts to bring human-produced emissions under control are faltering.

The best available evidence suggests the amount of the gas in the air has not been this high for at least three million years, before humans evolved, and scientists believe the rise portends large changes in the climate and the level of the sea.

In recent years the changes underway from this blink-in-geologic-time transformation of the atmosphere have become obvious, especially the patterns of extreme weather and precipitation changes that have long been the most confident predictions of climate science.

But some of the most profound changes will only come about as the new heat currently being trapped works its way thru the system, the oceans in particular, ripples through various “feedbacks” in the system, and reaches a point of equilibrium.
In that light, new research shines a light on what enormous impacts the carbon already released in to the atmosphere will have.

Christian Science Monitor:

Working with a continuous record of Arctic climate reaching back 3.6 million years, researchers have documented a period when the region was significantly warmer and wetter than it is today and when the atmosphere’s inventory of carbon dioxide was comparable to today’s levels.

Temperatures were high enough – about 14 degrees warmer than today in the warmest month of the summer – to suggest that the climate system is more sensitive to small changes in greenhouse-gas concentrations than the sensitivity estimates included in some climate models.

If that’s the case, as other paleoclimate studies have indicated, the models may be underestimating the amount of warming likely to result from increasing atmospheric CO₂ concentrations, the scientists say.

So even as the climate denial meme du jour has been that ‘climate sensitivity may not be as high as we thought”, these reconstructions from an era when co2 was not much greater than our own, must give us a sobering reality check.

The report found conditions much warmer than might have been predicted by atmospheric models, noting “..these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences.”

A climate feedback would be, for instance, as arctic ice melts and is replaced by open water, the open water absorbs much more solar heat than the bright reflective ice. This creates a vicious cycle, or “feedback”, reinforcing itself.

Planetsave:

“One of our major findings is that the Arctic was very warm in the middle Pliocene and Early Pleistocene [~ 3.6 to 2.2 million years ago] when others have suggested atmospheric CO2 was not much higher than levels we see today. This could tell us where we are going in the near future. In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier climate models,” the authors state.

LATimes:

The findings, based on sediment cores drilled from a Russian lake, don’t bode well for the current model of human-forced climate change, the researchers warn. They suggest that climate changes will be more amplified in the northern latitudes than currently predicted…

One of the clearest warning signs that this may be the case in our own time period is the rapid decline of arctic sea ice, that is now running 60 some years ahead of what would have been thought a “worst case” scenario, just a few years ago.